Dinosaurs’ death cleared way for swift rise of frogs

New York, July 4 (IANS) The asteroid or comet strike that wiped out three-fourths of life on Earth, including non-avian dinosaurs, set the stage for the swift rise of frogs, according to a new study.

If the calamity had not wiped the planet clean of most terrestrial life 66 million years ago, 88 per cent of today’s frog species would not be here, said the study published in the journal Proceedings of the National Academy of Sciences.

“Frogs have been around for well over 200 million years, but this study shows it wasn’t until the extinction of the dinosaurs that we had this burst of frog diversity that resulted in the vast majority of frogs we see today,” said study co-author David Blackburn from Florida Museum of Natural History on the University of Florida campus in the US.

New frog species likely radiated rapidly throughout the world because so many environmental niches were available after the animals occupying them disappeared, study co-author David Wake, Professor at the University of California, Berkeley, said.

“We think there were massive alterations of ecosystems at that time, including widespread destruction of forests,” Blackburn pointed out.

“But frogs are pretty good at eking out a living in micro-habitats, and as forests and tropical eco-systems rebounded, they quickly took advantage of those new ecological opportunities,” he explained.

Frogs eventually rose to become one of the most diverse groups of vertebrates, with more than 6,700 described species.

But sparse genetic data has hindered scientists from reliably tracing their evolutionary history and the links between frog families.

To tackle the mystery of frog evolution, the team sampled a core set of 95 nuclear genes from 156 frog species, combining this with previously published genetic data on an additional 145 species to produce the strongest-supported evolutionary tree, or phylogeny, to date.

The tree represents all 55 known families of frogs and generates a new timeline of frog evolution.

The researchers then used fossil records to translate genetic differences between frog lineages into dates at which they likely diverged from one another.

Their analyses showed three major lineages of modern frogs — about 88 per cent of living species — appeared simultaneously, evolving on the heels of the extinction event that marked the end of the Cretaceous Period and the beginning of the Paleogene 66 million years ago.

The team concluded that perhaps 10 groups of frogs survived the extinction, but only three of them (Hyloidea, Microhylidae and Natatanura) flourished and diversified to claim habitats and niches around the world.